CEF speed contest Design Discussions (2014)

Here are my lead-outs. .015" stranded SS through tiny brass tubes that were ready-length from a K & S assortment bag of "cut-offs" sold through Tower Hobbies. I had to use a lighted magnifier to make these.




Not sure where to put the bell-crank though. I found a length of 1/16" music-wire for the pushrod.. and proceeded to shear-it in the cutting-jaws of my locking pliers and.. snap!... both pieces grenaded and one piece is lost in the abyss. The second shearing was done by stepping with shoes on both sides of the pliers while on a rug. This yielded a couple lengths at the extremes of where the bell-crank might/could/should be mounted..

forward.. might help in leading/whipping.. until enough airspeed is attained? I keep thinking that I need to be in control of the nose of this model.. because it's going to be more about aiming the thrust.. rather than counting on stability from the airframe. Lead-out guides have free reign of placement along the tip-tanks.. no matter where the bell-crank is positioned.




Now I need to devise a mount for the capsule that will hold the balloon tank. I'm considering two fuse-mounted music-wire stand-offs with hoops to support the tube away from the fuse a bit, to prevent turbulence.

Looking good Roddie and also you will use those eye pins that I cant find around here Can't wait to see what you come up with at the tank tip , I know it will bee interesting . eric

getback wrote:Looking good Roddie and also you will use those eye pins that I cant find around here Can't wait to see what you come up with at the tank tip , I know it will bee interesting . eric

Thank You Eric! Those eye-pins you can find in Wal-Mart's jewelry dept. They're pretty small though.. better suited to .047" (3/64") wire and under. I'm running a 1/16" dia. pushrod and will probably use a small cut-off safety-pin. Like I said; it's mostly a weight-gain move for the tail.. if I need it.

You didn't need to cut wire to start this.

Put the engine on. Use clay and balance the model roughly where it should, between the LE and 20% typical. Hang it from a thread and see where the LO approximately should be. Put the LO position as the forward position on the bell crank location if convenient.

Bell crank location is important for FAIRNESS of the lead outs and has no other function in trim. The bell crank location with respect to CG is moot. Lead out position through the wing tip (or even off the wing tip) is what trims how the model flies. There are old designs that recommended using bent tubing and going pull-pull direct to the elevator!

Phil

Thanks Phil. I decided to worry less about it.. and move on. I cut 1/32" ply caps for both tip-tanks. They're dual-purpose. They cover the slot in the balsa.. and provide some rigidity for whatever I come up with for line-guides. The scale tip-tanks both have a small horizontal rear fin. My outboard-fin will be aluminum.. and serve as the tip weight.



I've mentioned this tool before. I like the way it quickly "carves" a rough-taper onto the edge of 1/8" balsa sheet.  The carbide blades remove wood scary-quick and it takes a little practice. I've found what works best is smooth strokes with even pressure.. not necessarily light pressure either. It depends on the density of the wood. A few quick strokes with a sanding-block afterward.. and you have a nice taper. I did this edge free-hand.. but the tool can alternately be placed in a vise.



Keeping the workpiece square to the cutters is naturally important.. so I took a measurement between the tool's guide.. and made a pair of pads to gage the gap closer to the thickness of the wood. 1/64" plywood scotch-taped on each side fit nicely.





Start by carving any existing corners of the work-piece first.. by pulling the stock completely through the cutters from an inch or so back. It's easier than starting in the middle and working your way outward.

I picked up some paint for Blue Angels trim.





The blue looks a little dark.. but I think it'll be ok.